I would strongly recommend to read next article -
"What does randomness look like"It explains that long streaks of nothing are best proof that guild shop is indeed random.
Even you say - "In my guild i hear the others are doing well", it means that you think that PM lowered rates from shop only for you?)
Nope, it's just unlucky situation. I also had 2 month of empty shop and then 2 Zeus in 3 days.
Don't look at shop as card source. See it as rare bonus that sometime give cards, but mostly give nothing.
Midas aka Howrus. GM of Fairy Tails.